In an emergency stop situation of an elevator the elevator car is stopped by disconnecting the supply of electric power to the electric motor of the hoisting machine of the elevator, as well as simultaneously connecting machinery brakes, of which there are usually two, to brake the traction sheave of the hoisting machine.
Different elevators can be counterweighted for different loads. The load of the elevator also varies from one run to another. Consequently, during an emergency stop the imbalance of forces varies. It follows from the variation in the imbalance of forces that during an emergency stop also the deceleration of the elevator car varies, in which case an emergency stop can, depending on the situation, result in either excessive or insufficient deceleration of the elevator car.